All The World's Primates

World Population of the Endangered Western Hoolock Gibbons Now Less than Previously Thought

June 01, 2011

Eastern hoolock
gibbon female
(Hoolock leuconedys)

Rekha Chetry Ph.D and Dilip Chetry,Ph.D

The endangered western hoolockgibbon's (Hoolock hoolock)
world population is now less than previously estimated. This lesser ape and close relative to man, known for its beautiful songs, was thought
to be the only gibbon in Assam, India. Assam was thought to be one of the few places where
it still had a viable population.

We surveyed six forest reserves in
Sadiya, a part of Tinsukia district on the extreme east boundary of
Assam. Instead of the western hoolock, we determined that the gibbon population is the vulnerable eastern gibbon (Hoolock
leuconedys). A total of 33 individuals in 10
groups were recorded from direct sighting. We estimate the occurrence of
another 16 groups from calls counted. The average group size was 3 with
individuals ranging from 1 to 5. Sadly our survey found no gibbons
present in 3 of the 6 forest reserves.

And these eastern hoolocks are under threat. The
reserves, unlike a sanctuary or national park, do not enjoy strong
legal protection and face numerous threats, including hunting, illegal
logging, commercial harvesting of bamboo, cane, ferns, tora, and cattle
grazing. Almost half of the forest reserve land is under
encroachment with 6070 hectares out of 12,512 lost. This is due to a lack
of community awareness and inadequate protection. The forest department has a staff of only 8
people to combat illegal activities and there are no staff quarters or
offices in any of the reserves.

We
initiated the first education and awareness program and our new findings
received wide media coverage. We plan to recommend that the 3 reserve
forests become wildlife sanctuaries with the eastern hoolock gibbon as a
flagship species for conservation.